As is known in the art, a field seed planter includes a group of seed chutes or seed discharge tubes, one for each row to be simultaneously planted. Each of these seed chutes or tubes convey individual seeds from a seed dispenser in conjunction with a hopper or other seed supply to individual furrows formed in the ground by the planter as it moves across a field. Various monitoring and counting arrangements have been utilized for obtaining a count of the number of seeds dispensed by such seed planters. Such counting is particularly useful in determining and controlling the density or population of seeds planted in order to optimize crop yield. Additionally, seed spacing information is of interest because yield is positively affected by the uniform spacing of such seeds.
One type of seed planter generally utilizes photoelectric devices to sense the passage of individual seeds through the seed chutes or tubes. Such arrangements generally include a light source such as a light emitting diode (LED) positioned to one side of the seed chute or tube and a light responsive element such as a photoresponsive transistor or photovoltaic cell positioned at the opposite side of the tube. Hence, the photoresponsive element normally produces a steady state signal level in response to the light incident thereupon from the light source. As a seed passes through the chute and comes between the light source and light responsive element, the level of light incident upon the light responsive element momentarily decreases. Responsively, the light responsive element produces a momentary change in the normal or steady state signal level output, which represents potentially a seed.
However, various challenges to accuracy of seed counting are encountered including considerable dirt, dust and the like as the planter moves through the field. As the seeds move through the chute, the density of seeds can also result in more of a flow of seeds and not a one-by-one feed and photoresponsive systems may not accurately detect and count a flow of seeds. Moreover, various coatings are commonly provided on seed grains, and these coatings often accumulate in the seed chutes or tubes. Accordingly, the foregoing accumulations of material in the seed tube tend to interfere with proper operation of the photoresponsive system.
Another type of seed sensor utilizes microwave energy. This type of sensor provides a waveguide intersecting a portion of the path of travel of seeds for supporting the propagation of a standing wave pattern of microwave energy. Generally speaking, this apparatus detects disturbances in this standing wave pattern due to the passage of seeds through the seed channel, and in particular through the portion thereof in which the waveguide is located. Associated circuitry is responsive to these disturbances or changes in microwave energy in the waveguide for determining the presence or absence of seeds, as well as in some instances for counting the seeds. One such microwave seed sensor apparatus is shown for example in U.S. Pat. No. 4,246,469 to Merlo, and another such microwave seed sensing apparatus is shown in U.S. Pat. No. 4,239,010 to Amburn.
This type of technology generally makes use of the dielectric properties of seeds and/or other material or articles flowing along a path of travel to provide for detection of such seeds, material or other articles. Generally speaking, an electromagnetic field is set up transversely of the path of travel, such as in the seed chute or channel and detects changes in the electromagnetic field due to the passage of such seeds or other discrete articles or the flow of material therethrough. More particularly, in a case of seeds or articles or materials having measurable dielectric properties, a sensor having primarily capacitive or capacitance-like properties, at a low frequency, may be utilized such as a pair of conductive plates being placed on either side of the path of travel in a seed tube. These plates generally define plates of a capacitor with the seed channel portions therebetween comprising the dielectric portion of the capacitor. Hence, if an object or material of a different relative permittivity or dielectric property relative to air enters this field, the electric field state will be altered. The resulting alteration can be separated into both a transient effect and steady state effect where the transient effect is generally much less pronounced than the steady state effect and of much shorter time duration.
Existing RF sensors suffer from low signal to noise ratio thus limiting sensitivity to small seeds. Existing RF sensors do not use differential detection or phase sensing of the reflected signal.
Some of these seed counting systems, although somewhat reliable, may still encounter challenges with relatively small seeds such as Milo and high seed rate seeds such as soybeans, with overlapping seeds such as Hilldrop Cotton, or with dealing with dust and distinguishing it from the seeds.